"This study actually found more unsuspected cancers outside of the colon than within it and often at early, curable stages," says Pickhardt.

Pickhardt's research team reviewed the medical records of 10,286 adults, 5388 men and 4898 women, who had a virtual colorectal cancer screening.

The study found unsuspected cancer in 58 patients; 22 had colorectal cancer and virtual colonoscopy detected a cancer outside the colon in 36 people, including renal cell cancer, lung cancer and non-Hodgkin's lymphoma. Virtual colonoscopy allows limited views of areas outside the colon including the abdomen, pelvis and parts of the lungs. Optical colonoscopy can only provide an assessment of the colon itself.

"Nearly all of the cancers were localized or detected at an early stage," says Pickhardt. "The results suggest that early detection of asymptomatic extra-colonic cancer represents an additional benefit of screening CT colongraphy that is not available with optical colonoscopy."

The less invasive virtual colonoscopy doesn't require a scope or intravenous sedation. The procedure costs less than optical colonoscopy and takes 10 minutes or less.

"Virtual colonoscopy is an accurate, safe and convenient screening test that could be a life-saving examination," says Pickhardt.